Federal scientists say they've come up with the first way to reliably predict the spread of wildfires and to continually update their forecasts for the benefit of fire fighters.

The technique involves sophisticated new computer models that use everything from satellite images of active fires to the latest weather reports and information on the way a fire is behaving. The advance was produced by the National Center for Atmospheric Research and the University of Maryland and published in the journal Geophysical Research Letters.

Janice Coen, an NCAR scientist who co-authored the study, discussed the advance with U-T San Diego by email. The text has been edited for continuity.

In October 2003, motorists were forced to drive on the embankment of Interstate 15 when the Cedar Fire crossed the freeway.
USMC

In October 2003, motorists were forced to drive on the embankment of Interstate 15 when the Cedar Fire crossed the freeway.

Q: Could you tell me how much this new modeling will improve the ability to forecast the growth of wildfires in areas like Southern California?

A: This could be a tremendous improvement for modeling the growth of both types of Southern California wildfires (those being Santa Ana events and events like the Station Fire or Zaca Fire, which occurred in heavy fuels but without strong environment winds). That is because current tools simply estimate how fast the leading edge of a fire will spread, usually with one wind measurement, which might be far away, and a map of fuel and terrain.

The modeling I do combines a very high resolution weather model with fire behavior components. So, not only does our model capture the complicated wind speed-ups and the areas where there are no winds created, it captures the interactions between weather and the fire - how the fire 'creates its own weather'.

This happens because the winds direct where the fire goes and how fast it consumes the fuel (vegetation), which releases heat that causes air to rise. As the air rises in a column, it pulls in air at the base to replace the rising air. This changes the winds near the fire. These fire-induced winds are what drive fires like Zaca and Station. There may be weak or no wind all around the fires, so the simple tools currently in use are unable to predict where they will go because no station will capture these strong winds within the fire.

Arcing power lines, buffeted by Santa Ana winds, were blamed by investigators for the Oct. 21, 2007 Witch Creek fire in San Diego County. The fire started near Santa Ysabel, burned from Julian to Rancho Bernardo and was the largest of the many wildfires to ravage Southern California in 2007. The Witch Creek fire destroyed 1,125 residential structures. Suppression efforts cost more than $18 million. Forty-five firefighters were injured. Two people died.
Union-Tribune

Arcing power lines, buffeted by Santa Ana winds, were blamed by investigators for the Oct. 21, 2007 Witch Creek fire in San Diego County. The fire started near Santa Ysabel, burned from Julian to Rancho Bernardo and was the largest of the many wildfires to ravage Southern California in 2007. The Witch Creek fire destroyed 1,125 residential structures. Suppression efforts cost more than $18 million. Forty-five firefighters were injured. Two people died.

Q: What's most responsible for this advance?

A: We have been developing the model's ability to reproduce past events well over the past 15 years. This work turns the corner toward using it as a forecast into the future ... Using these more sophisticated models that include a weather model has brought a tremendous advance; they are able to reproduce where a fires goes and the sudden changes that are so dangerous for firefighters (such as) wind shifts caused by the fire-weather interactions I just mentioned, blowups where the winds (including the effects from the fire) combine to suddenly cause the fire to spready rapidly.

On the other hand, it introduced challenges that all weather models face. For example, all weather models become less accurate with time. How would one model a fire event that lasts weeks or even months? The transformative event that makes this possible is the new satellite data that maps the fire in so much greater detail that we can routinely (two two times a day) clearly see the fire perimeter. Before, we would have to model the fire from ignition, which might smolder for several days, burn a couple days, rest a couple days, then burn again. By that time, the accuracy of the weather in the simulation, and therefore where it had directed the fire, was very bad.